boring cylinder

[trouble661]

my 400ex is starting to burn a little oil. and am wanting to rebuild. correct me if I am wrong. i am wanting to go .080 over which i think is a 416cc. doesnt there have to be so much clearance between the sleeve and piston?. if so how much. i need to know what to tell the guy at the bore shop.

[JD400exrider]

You want to take the new piston / rings with the cylinder to the machine shop. They will take it from there.

[david kelsch]

I NOTICED ON MY WISECO PISTON BOX IT HAD THAT INFORMATION PRINTED ON THE LABEL BELOW THE PART NUMBER. CANT REMEMBER WHAT IT SAID THOUGH.

[F-16Guy]

The clearance will be marked on the box. A good machine shop won't even bore your cylinder without the new piston for reference. You can have them gap the rings or you can do it yourself, the rings will come with instructions for that. All you do is slide the top ring down in the new bore and square it up by sliding the piston up underneath it. Now check the gap. The instructions will tell you how much gap there should be, but as a rule of thumb there should be about .004 gap per inch of bore (3 1/2" bore=approx 0.014 gap). File as necessary to obtain the desired gap, and make sure to remove any burrs with a piece of emery cloth. Repeat with second ring. Only the top two rings get gapped, the oil ring (bottom groove) does not. Make sure to lube the rings and cylinder with a light coat of motor oil before sliding the rings into the bore, you don't want any scores or gouges.

[2004TRX450R]

They can't really bore it unless you bring them the piston. They have to have it to match the bore to the piston. If they don't ask for the piston take it to another shop. Also if they know what they are doing at all they should know what the clearance should be. I think on something like a 400EX there should probably be between .0015" and .002" piston to cylender clearance.